Molecular Changes in Children with Heart Failure Undergoing Left Ventricular Assist Device Therapy

Durable left ventricular assist device explantation following recovery in paediatric patients: Determinants and outcome after explantation

OBJECTIVES

Myocardial recovery in children supported by a durable left ventricular assist device is a rare, but highly desirable outcome because it could potentially eliminate the need for a cardiac transplant and the lifelong need for immunosuppressant therapy and the risk of complications. However, experience with this specific outcome is extremely limited.

METHODS

All patients < 19 years old supported by a durable left ventricular assist device from the European Registry for Patients with Mechanical Circulatory Support database were included. Participating centres were approached for additional follow-up data after explantation. Associated factors for explantation due to myocardial recovery were explored using Cox proportional hazard models.

RESULTS

The incidence of recovery in children supported by a durable left ventricular assist device was 11.7% (52/445; median duration of support, 122.0 days). Multivariable analyses showed body surface area (hazard ratio 0.229; confidence interval 0.093-0.565; P = 0.001) and a primary diagnosis of myocarditis (hazard ratio 4.597; confidence interval 2.545-8.303; P < 0.001) to be associated with recovery. Left ventricular end-diastolic diameter in children with myocarditis was not associated with recovery. Follow-up after recovery was obtained for 46 patients (88.5%). Sustained myocardial recovery was reported in 33/46 (71.7%) at the end of the follow-up period (28/33; >2 year). Transplants were performed in 6/46 (11.4%) (in 5 after a ventricular assist device was reimplanted). Death occurred in 7/46 (15.2%).

CONCLUSIONS

Myocardial recovery occurs in a substantial portion of paediatric patients supported with durable left ventricular assist devices, and sustainable recovery is seen in around three-quarters of them. Even children with severely dilated ventricles due to myocarditis can show recovery. Clinicians should be attentive to (developing) myocardial recovery. These results can be used to develop internationally approved paediatric weaning guidelines.

Single Nuclei Sequencing Reveals Novel Insights Into the Regulation of Cellular Signatures in Children With Dilated Cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is a leading cause of death in children with heart failure. The outcome of pediatric heart failure treatment is inconsistent, and large cohort studies are lacking. Progress may be achieved through personalized therapy that takes age- and disease-related pathophysiology, pathology, and molecular fingerprints into account. We present single nuclei RNA sequencing from pediatric patients with DCM as the next step in identifying cellular signatures.

METHODS

We performed single nuclei RNA sequencing with heart tissues from 6 children with DCM with an age of 0.5, 0.75, 5, 6, 12, and 13 years. Unsupervised clustering of 18 211 nuclei led to the identification of 14 distinct clusters with 6 major cell types.

RESULTS

The number of nuclei in fibroblast clusters increased with age in patients with DCM, a finding that was confirmed by histological analysis and was consistent with an age-related increase in cardiac fibrosis quantified by cardiac magnetic resonance imaging. Fibroblasts of patients with DCM >6 years of age showed a profoundly altered gene expression pattern with enrichment of genes encoding fibrillary collagens, modulation of proteoglycans, switch in thrombospondin isoforms, and signatures of fibroblast activation. In addition, a population of cardiomyocytes with a high proregenerative profile was identified in infant patients with DCM but was absent in children >6 years of age. This cluster showed high expression of cell cycle activators such as cyclin D family members, increased glycolytic metabolism and antioxidative genes, and alterations in ß-adrenergic signaling genes.

CONCLUSIONS

Novel insights into the cellular transcriptomes of hearts from pediatric patients with DCM provide remarkable age-dependent changes in the expression patterns of fibroblast and cardiomyocyte genes with less fibrotic but enriched proregenerative signatures in infants.

Pathophysiology and molecular signalling in pediatric heart failure and VAD therapy

Heart Failure (HF) is a progressive clinical syndrome characterized by molecular and structural abnormalities that result in impaired ventricular filling and a reduced blood ejection. In pediatric patients, HF represents an important cause of morbidity and mortality, but underlying cause, presentation and disease course remains unclear in many cases. It is evident that a child is not a "small adult" and findings are not comparable. The adoption of a standardized clinical and surgical tools as well as increased biomolecular research and therapeutic trials targeting pediatric patients with HF would greatly improve the management of this special class of patients. This review examines the most current information about the pathophysiology and molecular mechanisms related to HF in children to identify gaps in our knowledge base to further improve clinical care and outcomes.

Control of cytokinesis by β-adrenergic receptors indicates an approach for regulating cardiomyocyte endowment

One million patients with congenital heart disease (CHD) live in the United States. They have a lifelong risk of developing heart failure. Current concepts do not sufficiently address mechanisms of heart failure development specifically for these patients. Here, analysis of heart tissue from an infant with tetralogy of Fallot with pulmonary stenosis (ToF/PS) labeled with isotope-tagged thymidine demonstrated that cardiomyocyte cytokinesis failure is increased in this common form of CHD. We used single-cell transcriptional profiling to discover that the underlying mechanism of cytokinesis failure is repression of the cytokinesis gene ECT2, downstream of β-adrenergic receptors (β-ARs). Inactivation of the β-AR genes and administration of the β-blocker propranolol increased cardiomyocyte division in neonatal mice, which increased the number of cardiomyocytes (endowment) and conferred benefit after myocardial infarction in adults. Propranolol enabled the division of ToF/PS cardiomyocytes in vitro. These results suggest that β-blockers could be evaluated for increasing cardiomyocyte division in patients with ToF/PS and other types of CHD.

Exosomes from pediatric dilated cardiomyopathy patients modulate a pathological response in cardiomyocytes

Stimulation of the renin-angiotensin-aldosterone system (RAAS) and β-adrenergic receptors plays an important role in adult heart failure (HF). Despite the demonstrated benefits of RAAS inhibition and β-adrenergic receptor blockade in adult HF patients, no substantial improvement in survival rate has been observed in children with HF. This suggests that the underlying disease mechanism is uniquely regulated in pediatric HF. Here, we show that treatment of human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) and neonatal rat ventricular myocytes (NRVMs) with serum from pediatric dilated cardiomyopathy (DCM) patients induces pathological changes in gene expression, which occur independently of the RAAS and adrenergic systems, suggesting that serum circulating factors play an important role in cardiac remodeling. Furthermore, exosomes purified from DCM serum induced pathological changes in gene expression in NRVMs and iPSC-CMs. Our results suggest that DCM serum exosomes mediate pathological responses in cardiomyocytes and may propagate the pediatric HF disease process, representing a potential novel therapeutic target specific to this population.NEW & NOTEWORTHY The results of this work could alter the present paradigm of basing clinical pediatric heart failure (HF) treatment on outcomes of adult HF clinical trials. The use of serum-treated primary cardiomyocytes may define age-specific mechanisms in pediatric HF with the potential to identify unique age-appropriate and disease-specific therapy.